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    Contents of /trunk/grub/patches/grub-2.02-binutils-2.27-support-modules-without-symbol-table.patch

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    Revision 2900 - (show annotations) (download)
    Tue Apr 4 09:31:09 2017 UTC (7 years ago) by niro
    File size: 4440 byte(s) 
    -renamed
    1 [PATCH v2] support modules without symbol table
    2
    3 From: Andrei Borzenkov
    4 Subject: [PATCH v2] support modules without symbol table
    5 Date: Wed, 3 Feb 2016 20:01:24 +0300
    6 all_video module does not have any code or data and exists solely for
    7 .moddeps section to pull in dependencies. This makes all symbols unneeded.
    8
    9 While in current binutils (last released version as of this commit is 2.26)
    10 ``strip --strip-unneeded'' unintentionally adds section symbols for each
    11 existing section, this behavior was considered a bug and changed in commit
    12 14f2c699ddca1e2f706342dffc59a6c7e23e844c to completely strip symbol table
    13 in this case.
    14
    15 Older binutils (verified with 2.17) and some other toolchains (at least
    16 elftoolchain r3223M), both used in FreeBSD, remove symbol table in all_video
    17 as well.
    18
    19 Relax run-time check and do not return error for modules without symbol table.
    20 Add additional checks to module verifier to make sure such modules
    21
    22 a) have non-empty .moddeps section. Without either externally visible symbols
    23 or .moddeps modules are completely useless and should not be built.
    24
    25 b) do not have any relocations.
    26
    27 Closes: 46986
    28
    29 v2: add run-time check for empty symbol table if relocations are present as
    30 suggested by Vladimir.
    31
    32 ---
    33 grub-core/kern/dl.c | 8 +++++++-
    34 util/grub-module-verifierXX.c | 19 ++++++++++++++++++-
    35 2 files changed, 25 insertions(+), 2 deletions(-)
    36
    37 diff --git a/grub-core/kern/dl.c b/grub-core/kern/dl.c
    38 index 59a6ef4..e394cd9 100644
    39 --- a/grub-core/kern/dl.c
    40 +++ b/grub-core/kern/dl.c
    41 @@ -333,8 +333,11 @@ grub_dl_resolve_symbols (grub_dl_t mod, Elf_Ehdr *e)
    42 if (s->sh_type == SHT_SYMTAB)
    43 break;
    44
    45 + /* Module without symbol table may still be used to pull in dependencies.
    46 + We verify at build time that such modules do not contain any relocations
    47 + that may reference symbol table. */
    48 if (i == e->e_shnum)
    49 - return grub_error (GRUB_ERR_BAD_MODULE, N_("no symbol table"));
    50 + return GRUB_ERR_NONE;
    51
    52 #ifdef GRUB_MODULES_MACHINE_READONLY
    53 mod->symtab = grub_malloc (s->sh_size);
    54 @@ -576,6 +579,9 @@ grub_dl_relocate_symbols (grub_dl_t mod, void *ehdr)
    55
    56 if (seg)
    57 {
    58 + if (!mod->symtab)
    59 + return grub_error (GRUB_ERR_BAD_MODULE, "relocation without
    60 symbol table");
    61 +
    62 err = grub_arch_dl_relocate_symbols (mod, ehdr, s, seg);
    63 if (err)
    64 return err;
    65 diff --git a/util/grub-module-verifierXX.c b/util/grub-module-verifierXX.c
    66 index f612d51..f8c15b0 100644
    67 --- a/util/grub-module-verifierXX.c
    68 +++ b/util/grub-module-verifierXX.c
    69 @@ -176,7 +176,7 @@ get_symtab (const struct grub_module_verifier_arch *arch,
    70 Elf_Ehdr *e, Elf_Word
    71 break;
    72
    73 if (i == grub_target_to_host16 (e->e_shnum))
    74 - grub_util_error ("no symbol table");
    75 + return NULL;
    76
    77 sym = (Elf_Sym *) ((char *) e + grub_target_to_host (s->sh_offset));
    78 *size = grub_target_to_host (s->sh_size);
    79 @@ -191,7 +191,21 @@ check_symbols (const struct grub_module_verifier_arch
    80 *arch, Elf_Ehdr *e)
    81 Elf_Word size, entsize;
    82 unsigned i;
    83
    84 + /* Module without symbol table and without .moddeps section is useless
    85 + at boot time, so catch it early to prevent build errors */
    86 sym = get_symtab (arch, e, &size, &entsize);
    87 + if (!sym)
    88 + {
    89 + Elf_Shdr *s = find_section (arch, e, ".moddeps");
    90 +
    91 + if (!s)
    92 + grub_util_error ("no symbol table and no .moddeps section");
    93 +
    94 + if (!s->sh_size)
    95 + grub_util_error ("no symbol table and empty .moddeps section");
    96 +
    97 + return;
    98 + }
    99
    100 for (i = 0;
    101 i < size / entsize;
    102 @@ -243,6 +257,8 @@ section_check_relocations (const struct
    103 grub_module_verifier_arch *arch, void *e
    104 Elf_Word symtabsize, symtabentsize;
    105
    106 symtab = get_symtab (arch, ehdr, &symtabsize, &symtabentsize);
    107 + if (!symtab)
    108 + grub_util_error ("relocation without symbol table");
    109
    110 for (rel = (Elf_Rel *) ((char *) ehdr + grub_target_to_host (s->sh_offset)),
    111 max = (Elf_Rel *) ((char *) rel + grub_target_to_host (s->sh_size));
    112 @@ -272,6 +288,7 @@ section_check_relocations (const struct
    113 grub_module_verifier_arch *arch, void *e
    114 break;
    115 if (arch->short_relocations[i] == -1)
    116 grub_util_error ("unsupported relocation 0x%x", type);
    117 +
    118 sym = (Elf_Sym *) ((char *) symtab + symtabentsize * ELF_R_SYM
    119 (grub_target_to_host (rel->r_info)));
    120
    121 if (is_symbol_local (sym))
    122 --
    123 tg: (7290bb5..) bug/46986 (depends on: master)
    124